An increase in the rate of polyamine biosynthesis is usually associated with increased cellular proliferation, suggesting that altered control of ornithine decarboxylase (ODC) and/or S-adenosylmethionine decarboxylase (SAMD) may account for the abnormal growth patterns of malignant cells. To learn more about the differences between normal and transformed cells in this basic metabolic pathway, the regulation of polyamine biosynthesis will be studied in hamster embryo and mouse Balb/c 3T3 cells in culture. The synthesis and accumulation of the polyamines, putrescine, spermidine and spermine, will be compared in normal cells, cells exposed to chemical carcinogens, and cells malignantly transformed by carcinogens. The ODC and SAMD activities and the polyamine concentrations under diffferent culture conditions will be determined for each cell type. The temporal relationship between an alteration in polyamine biosynthesis and the expression of malignant transformation will be assessed. The elucidation of how this critical metabolic pathway is involved in the expression and maintenance of the neoplastic phenotype should lead to rational approaches to the chemotherapeutic control of malignancy.